(A) Field of the Invention
The present invention relates to an integrated circuit probe card with a planarity adjusting mechanism, and more particularly to an integrated circuit probe card with a planarity adjusting mechanism capable of adjusting the coplanarity between an integrated circuit device under test and a probe assembly including several probes.
(B) Description of the Related Art
Generally, it is necessary to test the electrical characteristic of integrated circuit devices on the wafer level for checking whether the integrated circuit device satisfies the product specification. Integrated circuit device with electrical characteristic satisfying the specification will be selected to carry on the subsequent packaging process, and other devices will be discarded to avoid additional packaging cost. Another electrical property test will be performed on the integrated circuit device after the packaging process is completed and finally to sieve out the disqualified devices to increase the product yield. As a result, several testing processes need to be performed during the fabrication process of an integrated circuit device.
FIG. 1 is a schematic cross-sectional view of an integrated circuit probe card 10 according to the prior art. As shown in FIG. 1, the integrated circuit probe card 10 using three-piece configuration consists of a printed circuit board 20, a ceramic substrate 30 and a probe contactor 40. The printed circuit board 20 comprises a plurality of pads 22 and a plurality of conductive wires 24 electrically connecting the pads 22 to a test machine (not shown in FIG. 1). The probe contactor 40 comprises a plurality of probes 42, which is used to contact a device under test (DUT) 52, such as an integrated circuit device, on a wafer 50 and acquire the electrical properties thereof.
During the probing process, the plane 44 consisting of tips of the probes 42 must be substantially coplanar to another plane 56 consisting of pads 54 of the device under test 52 so that the probes 42 can apply contact force uniformly to corresponding pads 54 on the device under test 52 to pierce the oxide thereon. If the plane 44 is inclined to the plane 56 rather than parallel to the plane 56, some of the probes 42 can contact corresponding pads 54, while the other probes 42 cannot establish physical contact and cannot form electrical connection. As a result, it is impossible to measure the electrical properties of the device under test 52 accurately.
Whether or not the plane 44 is parallel to the device under test 52 primarily depends on the length difference between the probes 42 and the planar orientation of the probe holder 40. Before the probing process is conducted, the prior art planarizes the tip of the probes 42 by a sanding technique. However, as the design rule shrinks to small size and high density, the arrangement of the pad 54 becomes denser, and the arrangement of the probe 42 for contacting the pad 54 must be shrunk to small pitch and high density accordingly. The probe 42 with a shrunk arrangement tends to be abrasively worn off, it is because of sanding process may introduce a large process variation errors; therefore, the sanding technology for planarizing the tip of the probe 42 cannot be applied to the probe 42 arranged with the shrunk design rule. Currently, an elastic material is positioned between the probe holder 40 and the circuit board 20, and the elasticity of the elastic material can accommodate plane difference originating from the length difference of the probes 42.
In addition, the planarity of the probe holder 40 must be taken into account except for the difference in the lengths of the probes 42 so as to allow the probes 42 to apply force uniformly on the pads 54 of the device under test 52. The prior art uses a differential screw to adjust the planarity of the probe holder 40. U.S. Pat. No. 6,586,956 B2 discloses a test system with an adjustable plane mechanism, which adjusts the planarity of the probe holder by the fine adjustment of differential screws. However, the disclosure of U.S. Pat. No. 6,586,956 B2 can only fine-adjust the planarity of the probe holder entirely, and the contact force applied by each probe on the corresponding pad cannot be adjusted individually if there is difference between the lengths of the probes.
U.S. Pat. No. 6,246,247 discloses a probe card assembly that also uses a differential screw to finely adjust the planarity of the space transformer of the probe card. Furthermore, U.S. Pat. No. 6,246,247 also discloses an elastic connector directly soldered on the assembly, which contains a soft core and a hard shell cladding the soft core. When the differential screws are used to fine-adjust the planarity of the space transformer of the probe card assembly, the electrical connection between the parts of the probe card assembly can still be ensured by the elasticity of the elastic connector.
However, the above-mentioned prior art references are complicated and inconvenient in adjusting the coplanarity between the probe card and the device under test, therefore it is necessary to improve the design of the prior art.